In recent years, high integration and high density in semiconductor device demands smaller and smaller wiring patterns or interconnections and also more and more interconnection layers. Multilayer interconnections in smaller circuits result in greater steps which reflect surface irregularities on lower interconnection layers. An increase in the number of interconnection layers makes film coating performance (step coverage) poor over stepped configurations of thin films. Therefore, better multilayer interconnections need to have the improved step coverage and proper surface planarization. Further, since the depth of focus of a photolithographic optical system is smaller with miniaturization of a photolithographic process, a surface of the semiconductor device needs to be planarized such that irregular steps on the surface of the semiconductor device will fall within the depth of focus.
Thus, in a manufacturing process of a semiconductor device, it increasingly becomes important to planarize a surface of the semiconductor device. One of the most important planarizing technologies is chemical mechanical polishing (CMP). In the chemical mechanical polishing, while a polishing liquid containing abrasive particles, such as silica (SiO2), ceria (CeO2) or the like, therein is supplied onto a polishing surface of a polishing pad, a substrate such as a semiconductor wafer is brought into sliding contact with the polishing surface and polished by using a polishing apparatus.
The polishing apparatus which performs the above-mentioned CMP process includes a polishing table having a polishing surface, and a polishing head (top ring) for holding a substrate such as a semiconductor wafer. When the substrate is polished with such a polishing apparatus, the substrate is held and pressed against the polishing surface under a predetermined pressure by the polishing head. At this time, while a polishing liquid is supplied onto the polishing surface, the polishing table and the polishing head are respectively rotated to bring the substrate into sliding contact with the polishing surface, so that the surface of the substrate is polished to a flat mirror finish.
A polishing rate of the surface, being polished, of the substrate depends not only on a polishing load on the substrate against the polishing pad but also on a surface temperature of the polishing surface. This is because a chemical action of the polishing liquid on the substrate depends on a temperature. Therefore, in manufacturing of the semiconductor device, in order to increase the polishing rate of the surface, being polished, of the substrate and further to keep the polishing rate constant, it is considered to be important to keep the surface temperature of the polishing surface during polishing of the substrate at an optimum value.
Therefore, conventionally, a fluid passage for heat exchange medium is provided in the interior of the polishing table and cooling water serving as the heat exchange medium is flowed in the fluid passage to exchange heat between the heat exchange medium and the polishing table. Thus, thermal deformation of the polishing table due to frictional heat during polishing is prevented and the surface temperature of the polishing surface on the polishing table is adjusted.
As described above, since the polishing table is rotated, the cooling water needs to be delivered into the interior of the rotating polishing table. Therefore, a rotary joint is provided on the polishing table, and the cooling water is supplied from the outside into the fluid passage in the polishing table through a cooling water pipe and the rotary joint to perform heat exchange in the polishing table, and is then discharged to the outside. The cooling water which has been discharged to the outside is cooled in a chiller unit, and is supplied into the polishing table again (see Japanese Laid-open Patent Publication No. 10-235552).
However, torsional vibration is generated in the rotary joint or an abnormal sound is generated at an engagement part between the cooling water pipe and the polishing table depending on installation environment or operating condition (e.g. at the time of low-speed idling) of the polishing apparatus. If the operation of the polishing apparatus is continued under this circumstance, a fatigue failure of the above-mentioned parts provided in the cooling water supply passage may be caused or the pipes may be damaged due to sliding wear, possibly leading to leakage of the cooling water.